PROJECT SUMMARY Many developmental communication disorders, such as speech sound disorder, specific language impairment, and dyslexia, are associated with central auditory processing deficits that affect phonetic perception. Infants learn how to classify the phonemes of their native language(s) through exposure to speech in the first year of life, but surprisingly little is known about the neural mechanisms of this key developmental process. The overarching goal of this project is to understand how complex signals like speech shape cellular and circuit properties in the central auditory areas responsible for decoding them. This research uses the zebra finch, a well-established model for auditory processing and learning. Like speech, birdsong has a complex spectral and temporal structure, and young birds need to hear song for normal development of auditory perception. Using the zebra finch model enables an approach that combines strong experimental control of the acoustic structure, social context, and timing of song experience, with intracellular and extracellular electrophysiological measurements and analyses of protein expression and trafficking. During a critical stage in vocal development, neurons in a cortical-level area involved in auditory learning develop diverse intrinsic properties that influence how they process communication sounds. Aim 1 examines the acoustic stimuli required for this plasticity to occur. Aim 2 investigates the mechanism of this experience- dependent intrinsic plasticity. Aim 3 tests how experience affects auditory processing in noisy conditions. By identifying how the timing and structure of auditory experience shape development at the single-cell level in a well-described learning task, this research has significant implications for understanding how impoverished environments can lead to auditory processing deficits associated with a wide range of human communication disorders.